AQA AS Biology

Revision Notes

3.5.4 The Cardiac Cycle

The Cardiac Cycle

  • The contraction of the heart is called systole, while the relaxation of the heart is called diastole
  • Atrial systole is the period when the atria are contracting and ventricular systole is when the ventricles are contracting
  • Atrial systole happens around 0.13 seconds after ventricular systole
  • During ventricular systole, blood is forced out of the pulmonary artery (to the lungs) and aorta (to the rest of the body)
  • One systole and diastole makes a heartbeat and lasts around 0.8 seconds in humans. This is the cardiac cycle

Pressure changes

  • During systole and diastole, heart valves open and close as a result of pressure changes
  • Valves are an important mechanism to stop blood flowing backwards
  • During diastole, the heart is relaxing
    • The atrioventricular valves open and the semilunar valves are closed
  • During systole, the heart contracts and pushes blood out of the heart
    • During this time, the atrioventricular valves are closed and the semilunar valves are open

Pressure Changes in the Heart Table

Pressure Changes in the Heart Table, downloadable AS & A Level Biology revision notes

Pressure Changes in the Cardiac Cycle, downloadable AS & A Level Biology revision notes

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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